This invention relates to a releasable coupling device particularly for releasably connecting gripper rail parts of gripper rails in a transfer press. For performing a tool replacement, the tools, together with the associated gripper rail parts, are moved out of the press transversely to its length, while the unaffected gripper rail components remain in place.
In transfer presses, for advancing the workpieces from one stage to a successive stage, gripper rail transport systems are provided whose gripper rails extend along the entire length of the press. In performing tool replacement it has been inconvenient that, while the tool units could readily be moved out of the press, the gripper rails first had to be released from their drives and then had to be pulled out of the press in a direction parallel to their length (that is, parallel to the press length).
To overcome the above-outlined drawback, the gripper rails are conventionally subdivided and interconnected in such a manner that, upon release, the gripper rail component associated with the tool to be replaced, could be moved out of the work tool chamber together with the tool as a unit. For this purpose, for example, the abutting ends of the gripper rail parts are screwed to one another with the aid of splicer plates. The disadvantage of this arrangement resides in the fact that the connections are very unstable, they are not capable of carrying substantial transverse loads and further, the construction includes "loose components" during tool replacement which have to be set aside, thus risking damage or loss of such components.
According to another solution, eccentric tightening devices are used in which the ends of the individual gripper rail components are tightened face-to-face to one another. For this purpose, however, a precise fit was required and further, this construction is exposed to significant wear. Also, with this type of coupling, it is not feasible to obtain a sufficiently large separating clearance for moving out the rail portions on the supporting carriage. The result has been a complex disassembling operation requiring a significant amount of time for the tool replacement.
According to a significantly improved device, disclosed in German Pat. No. 3,300,227, on the end faces of gripper rail parts sleeve members are secured. In one sleeve member an expander mandrel is slidably arranged which extends, in the operative state, into the adjoining sleeve member. The expander mandrel provides, by means of pressing members, a form-fitting connection with grooves provided in the inner faces of the sleeve members. The manufacture of this construction, however, has been found to be extremely time-consuming and the device has a great number of components which, in order to permit a positive force transmission, have to be accurately machined.